The present invention relates to a position transmitter which determines the point of incidence of a light or particle beam for determining position.
Such position transmitters can be used, for instance, as length, area, coordinate, angle or velocity pickups.
Since such position transmitters are frequently used in equipment in which the further processing of the position signal takes place digitally, a series of position transmitters has been developed, in which the position of the light beam is read out in a digital code.
Position transmitters which read out the position of a light beam digitally and can be used, for instance, as either angle or length pickups are known, for instance, from German Patent Nos. 23 33 698, 23 35 942, or U.S. Pat. No. 4,439,672. In these position transmitters, a code disc or a code scale is used which, corresponding to the desired code, has regions which influence the incident light beam differently. This code disc or code scale is relatively movable with respect to a light receiver which is frequently equipped also with a scanning grid. In this manner, the position of the incident light beam can be read out in a digital code, for instance, a binary code, Binary Coded Decimal (BCD) or a Gray code or in another code.
From DE-OS No. 32 20 560, a photoelectric encoder has become known in which two optical grids are moved relatively to each other. One of the two grids is integrated here in the semiconductor material in which also the light receiving device is formed.
Although these known position transmitters can be fabricated comparatively cost-effectively, they have the disadvantage that they require mechanically moved parts which are trouble-prone particularly under rough environmental conditions.
Various proposals for position transmitters have therefore become known which give the point of incidence of a light or particle beam absolutely and digitally, and make do without moving parts.
In one of these proposals, a CCD (charge coupled device) is used. However, it is a disadvantage when CCD arrays are used, that the location information can be called up only serially, and that comparatively complicated electronic circuitry is required for reading the location information out.
Thus, in such systems, not only the amount of structural means is comparatively large; in addition, they also do not meet the increased speed requirements.
A further digital position transmitter has become known from DE-OS No. 32 05 402. In this digital position transmitter, a multiplicity of sensors are connected via operational amplifiers with special feedback arrangements to the lines of a digital bus. It is achieved by the feedback arrangements that the signal on the digital bus indicates the point of incidence in a digital code.
This digital length transmitter is very complicated particularly due to the use of an operational amplifier with a special feedback arrangement as well as of a transistor with several emitter terminals for each sensor, so that it has not yet been realized in practice to date.